Drive unit connected to a transmission output for producing forward and reverse drive

ABSTRACT

A drive unit located in a power path between a transmission output and the wheels of a vehicle for reversing the direction of the transmission output includes a gear set including an input driveably connected to the transmission output, and a gearset output alternately rotating in a forward rotary direction and an underdriven reverse rotary direction relative to the speed and direction of the transmission output. A drive mechanism transmits power between the gearset output and the wheels.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to transmitting rotating power in amotor vehicle driveline. More particularly, it pertains to reversing therotational direction of an input, between a transmission output,connected to the input, and the wheels of the vehicle.

2. Description of the Prior Art

The powertrain of a hybrid electric vehicle includes multiple powersources, an internal combustion engine (ICE), principally used whenhighway speeds are sustained; an electric motor for charging electricstorage batteries, and a traction motor for launching the vehicle, i.e.,for accelerating the vehicle from a stopped condition.

In an electric hybrid powertrain for a passenger car, reverse drive isusually produced by a small traction electric motor whose torquecapacity is relatively low and is unamplified by the powersplittransmission in the powertrain. The traction motor alone is driven inreverse to launch an electric hybrid vehicle in a reverse directionwithout assistance from the ICE or torque amplification provided by atransmission or transaxle.

An electric hybrid vehicle that is equipped with all-wheel drive (AWD)or four-wheel drive (4WD) and is expected to tow a heavy load or to beoperated on rough terrain may have inadequate reverse drive torquecapacity because the output torque of the traction motor is too low forthose operating conditions.

Adding reverse gearing to the transmission itself is difficult. There isa need in the industry to increase the magnitude of wheel torqueprovided in reverse drive especially in the powertrain of electrichybrid vehicle equipped with AWD or 4WD, which is expected to tow aheavy load or to be operated on rough terrain.

SUMMARY OF THE INVENTION

Rather than redesigning existing powersplit transmissions andtransaxles, it is an advantage of this invention that reverse gearmechanisms capable of amplifying torque produced by the traction motorare housed in the AWE or 4WD unit.

The reverse gearing is combined with a high range function, by whichpower is transmitted directly to the vehicle wheels withoutamplification, and a low range function, by which power is transmittedto the vehicle wheels after being amplified

It is yet another advantage that the reverse gearing can be combinedwith a planetary differential gear unit, which splits power from thetraction motor after being amplified by the gearing into a first portionthat is transmitted to the rear wheels and a second portion that istransmitted to the front wheels.

A drive unit located in a power path between a transmission output andthe wheels of a vehicle for reversing the direction of the transmissionoutput includes a gear set including an input driveably connected to thetransmission output, and a gearset output alternately rotating in aforward rotary direction and an underdriven reverse rotary directionrelative to the speed and direction of the transmission output. A drivemechanism transmits power between the gearset output and the wheels.

The scope of applicability of the preferred embodiment will becomeapparent from the following detailed description, claims and drawings.It should be understood, that the description and specific examples,although indicating preferred embodiments of the invention, are given byway of illustration only. Various changes and modifications to thedescribed embodiments and examples will become apparent to those skilledin the art.

DESCRIPTION OF THE DRAWINGS

These and other advantages will become readily apparent to those skilledin the art from the following detailed description of a preferredembodiment when considered in the light of the accompanying drawings inwhich:

FIG. 1 is a top view of a motor vehicle driveline that includes atransmission, transfer case, and rear differential or axle housing;

FIG. 2 is a schematic diagram showing a kinematic arrangement for adrive unit that produces forward and reverse drive in a high-range andlow-range;

FIG. 3 is schematic diagram showing a kinematic arrangement for a driveunit that produces forward and reverse drive and splits the input torquebetween front and rear wheels;

FIG. 4 is schematic diagram showing an alternate kinematic arrangementthat produces forward and reverse drive and splits the input torquebetween front and rear wheels of a front wheel drive; and

FIG. 5 is schematic diagram showing a kinematic arrangement for a driveunit that produces forward and reverse drive.

DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference now to the drawings and particularly to FIG. 1, thepowertrain of a motor vehicle includes front and rear wheels 10, 12, apower transmission 14 for producing multiple forward and reverse speedratios driven by an engine (not shown), and a transfer case 16 thatcontinuously driveably connects the transmission output to a rear driveshaft 18. The transfer case 16 selectively connects the transmissionoutput to both the front drive shaft 20 and rear drive shaft 18 whenfour-wheel drive operation is actuated. Shaft 18 transmits power to arear wheel differential mechanism 22, from which power is transmitteddifferentially to the rear wheels 12 through axle shafts 24, 26, whichare contained within a differential housing. The front wheels aredriveably connected to right-hand and left-hand halfshafts 32, 34, towhich power is transmitted from the front drive shaft 20 through a frontdifferential mechanism 36.

The transfer case assembly 16 continually transmits rotating power tothe rear driveshaft 18 and rear wheels 12, which comprise the primarypower path. The transfer case 16 intermittently transmits rotating powerto the front driveshaft 20 and the front wheels 10, which comprise thesecondary power path, when a clutch located in the transfer case isactuated.

In the electric hybrid powertrain for a passenger car, reverse drive isusually produced by a small traction electric motor whose torquecapacity is relatively low and is unamplified by the powersplittransmission in the powertrain. An electric hybrid vehicle that isequipped with AWD or 4WD and is expected to tow a heavy load or tooperate on rough terrain often has inadequate reverse drive torquecapacity because the output torque of the traction motor is too low forthose operating conditions.

To correct this deficiency, the drive unit 39 shown in FIG. 2 has theability to change the rotational direction of the rear driveshaft 18 andforward driveshaft 20 alternately between forward and reverse dependingon the state of a coupler 46. Drive unit 39 driveably connects thetransmission output 40 and the vehicle wheels 10, 12 similarly to thefunction of a transfer case. In addition, the torque produced at theoutput 40 of a transmission 42, such as a powersplit transmission for anelectric hybrid vehicle powertrain, can be amplified by the drive unit39. Input torque is alternately amplified or transmitted through driveunit 39 without amplification in accordance with the state of a coupler48. Power is transmitted continually to rear driveshaft 18, and power istransmitted to front driveshaft 20 in accordance with the state of acoupler 50 located in drive unit 39.

A reverse drive power path includes a pinion 52 secured to the driveunit input 44 and supported on a pilot bearing 53, gear 54 meshing withpinion 52 and secured to a layshaft 56, reverse pinion 58 secured tolayshaft 56, reverse idler 60 meshing with pinion 58 and supported on anidler shaft 62, coupler 46 secured to intermediate shaft 66, and reversegear 64 journalled on intermediate shaft 66 and meshing with idler 60.

When the selector sleeve 67 of coupler 46 is moved leftward causing itsdog teeth to engage dog teeth 68 formed on or secured to pinion 52,coupler 46 driveably connects intermediate shaft 66 directly to inputshaft 44 without a change in rotational direction. When the selectorsleeve 67 of coupler 46 is moved rightward causing its dog teeth toengage dog teeth 69 formed on or secured to gear 64, coupler 46driveably connects intermediate shaft 66 to gear 64 with a change inrotational direction. Reverse gear 64 is driven in the oppositedirection from the rotational direction of input shaft 44 through thepower path that includes pinion 52, gear 54, layshaft 56, reverse pinion58, idler 60, and gear 64. In this way, intermediate shaft 66 isunderdriven in a reverse direction relative to the direction and speedof input 44.

A power path for producing a low-range and high-range includes a pinion70, journalled on intermediate shaft 66; a double gear supported onlayshaft 56, which includes gear 72, meshing with pinion 70, and gear74, secured to gear 72; a pinion 76 meshing with gear 74 and journalledon output shaft 78; and coupler 48, secured to intermediate shaft 66.The rear driveshaft 18 is secured to output shaft 78. A pilot bearingmember 82 supports the end of intermediate shaft 66 and is secured tooutput shaft 78.

A 4×4 coupler 50, secured to output shaft 78, includes a selector sleevethat is moved leftward to its 4×4-state causing its dog teeth to engagedog teeth on pinion 74, thereby driveably connecting output shaft 78 andpinion 76. When the selector sleeve of coupler 50 is moved rightwardfrom its 4×4-state to its 4×2-state, its dog teeth disengage the dogteeth on pinion 76, thereby driveably disconnecting output shaft 78 andpinion 76.

When the selector sleeve of coupler 50 is in its 4×2-state and coupler48 is moved rightward to the high-range state causing its dog teeth toengage dog teeth on pilot bearing member 82, coupler 48 driveablyconnects intermediate shaft 66 and output shaft 78. With coupler 48 inthis high-range state, output shaft 78 is driven at the same speed androtational direction as those of intermediate shaft 66.

When the selector sleeve of a 4×4 coupler 50 is moved leftward to the4×4 state while the range coupler 48 is in the high-range state, poweris transmitted from intermediate shaft 66 through coupler 48, pilotbearing member 82, output shaft 78, and coupler 50 to pinion 76. Gears74 and 72 are then driven at the same speed and in the reverse directionfrom the speed and direction of intermediate shaft 66. Gear 72 drivesthe forward output gear 80 and forward driveshaft 20 in the samedirection and at the same speed as those of intermediate shaft 66.

When the selector sleeve of range coupler 48 is moved to the low-rangestate while the 4×4 coupler 50 is in the 4×4-state, power is transmittedfrom intermediate shaft 66 through coupler 48, pinion 70, gear 72,forward output gear 80 and forward driveshaft 20. Gear 72 then functionsas a reversing idler, such that output gear 80 and forward driveshaft 20are underdriven in the same direction as intermediate shaft 66.

FIG. 3 illustrates an alternate embodiment of the kinematic arrangementfor drive unit 39. The forward and reversing gear set and drive path,which includes input 44, pinion 52, pilot bearing 53, gear 54, layshaft56, reverse pinion 58, reverse idler 60, coupler 46 secured tointermediate shaft 66, and reverse gear 64, are substantially identicalto those of FIG. 2.

A planetary differential 90 in the form of a simple planetary gear setincludes a sun gear 92, secured to output shaft 78 and rear driveshaft18; a ring gear 94, secured to an output pinion 96; a carrier 98,secured to intermediate shaft 66; and a set of planet pinions 100,supported on carrier 98 and meshing with sun gear 92 and ring gear 94.Pinion 96 is in meshing engagement with an idler 102, which is engagedwith an output gear 104, secured to forward driveshaft 20.

The planetary differential 90 divides or splits the torque carried byintermediate shaft 66, one portion of the torque being transmitted tothe rear driveshaft 18 the other portion being transmitted to theforward driveshaft 20. The ratio of the pitch diameter of ring gear 94and that of sun gear 92 determines the relative magnitudes of thesetorque portions. The torque split produced by planetary differential 90is not an equal torque split. In the arrangement shown in FIG. 3, thegreater portion of the torque carried on intermediate shaft 66 istransmitted to ring gear 94 and front driveshaft 20 than is transmittedto sun gear 92 and rear driveshaft 18.

Alternatively, sun gear 92 can be driveably connected to frontdriveshaft 20 and ring gear 94 can be connected to the rear driveshaft88. In that arrangement, the greater portion of the intermediate shafttorque would be transmitted to the rear driveshaft 18 than to the frontdriveshaft 20.

The planetary differential 90 could be a bevel gear differentialmechanism, such as those used in an inter-wheel axle differential totransmit power differentially to left-side and right-side vehiclewheels.

Power from the differential 90 or an alternative differential mechanismcan be transmitted to the forward driveshaft 20 through a chain drivemechanism rather than the layshaft drive comprising pinion 96, idler 102and front output gear, illustrated in FIG. 3.

FIG. 4 illustrates a power take-off drive unit 108 applicable for use ina vehicle whose transmission 42 is arranged transversely with respect tothe longitudinal axis of the vehicle. The final drive gear 110 isdriveably connected to the input 112 of a forward and reversing gearset114. The power take-off unit 108 transmits power to the rear driveshaft18 and forward halfshafts 32, 34 through an inter-axle differential 116and an inter-wheel differential 118.

The power take-off unit 108 includes a reversing gearset 114, whichproduces forward or reverse output. The reversing gearset 114 comprisesa sun gear 120, secured to input shaft 112; a ring gear 122; a carrier124; and a set of planet pinions 126, rotatably supported on carrier 124and in meshing engagement with sun gear 120 and ring gear 122. Coupler130, secured to carrier 124, has a reversing state, in which carrier 124is held against rotation, and a forward drive state, in which thecarrier is released for rotation and driveably connected to ring gear122. The selector sleeve of coupler 130 moves leftward to the reversingstate, where its dog teeth engage dog teeth on a housing, and it movesrightward to its forward drive state, where its dog teeth engage dogteeth on the ring gear 122.

The output of the reversing gear set 114, ring gear 122, is driveablyconnected to an inter-axle differential 116, which divides its inputtorque into a portion transmitted to the front axles and a portiontransmitted to the rear axles. The inter-axle differential 116 includesa sun gear 134; a ring gear 138, driveably connected to a bevel pinion140; a carrier 142, driveably connected to ring gear 122; and a set ofplanet pinions 144, supported on carrier 142 and meshing with sun gear134 and ring gear 138. Bevel pinion 140 meshes with a rear output bevelgear 146, which is secured to rear driveshaft 18.

An inter-wheel differential 118 transmits its input torquedifferentially to the front axles 32, 34. The inter-wheel differential118 includes a housing secured to sun gear 134, the housing containing aleft side bevel gear 148 secured to the left halfshaft 34, a right-sidebevel gear 150 secured to the right halfshaft 32, and bevel pinions 152,154, which are driven by the housing of the inter-wheel differential 118and are engaged with bevel gears 148 and 150.

In operation, the input sun gear 120 of reversing gear set 114 is drivenby the final drive gear 110 of the transmission 42. When the selectorsleeve of coupler 130 moved to the reversing state, carrier 124 is heldagainst rotation and ring gear 122 is underdriven in the reversedirection relative to speed and direction of input shaft 112 and sungear 120. When the selector sleeve of coupler 130 is moved to theforward drive state, carrier 124 and ring gear 122 are mutuallydriveably connected, thereby locking up reversing gear set 114 anddriving ring gear 122 in the same direction and at the same speed asthose of input shaft 112 and sun gear 120.

Inter-axle differential 108 divides or splits the magnitude of torquetransmitted to carrier 142 by ring gear 122 into a torque portioncarried by ring gear 138 and a torque portion carrier by sun gear 134.In the embodiment illustrated in FIG. 4, a greater portion of the torquetransmitted by carrier 142 to the inter-axle differential 108 istransmitted to ring gear 138 and bevel pinion 140 and the reardriveshaft 18 than is transmitted to sun gear 134 and the inter-wheeldifferential 116.

However, the inter-axle differential 108 can be modified such that sungear 134 is driveably connected to bevel pinion 140 but not to thehousing of the inter-wheel differential 118, and ring gear 138 isdriveably connected to the housing of the inter-wheel differential 118but not to side bevel pinion 140. When the power path is arranged inthat way, a greater portion of the torque carried by carrier 142 istransmitted to the inter-wheel differential 116 than is transmitted tothe rear bevel pinion 140.

FIG. 5 illustrates an alternate forward drive and reversing kinematicarrangement for drive unit 39, in which the output shaft 40 oftransmission 42 is secured to the input 44 of the drive unit. Aplanetary gear set 151 is able to produce alternately forward andreverse output in accordance with the state of a coupler 152, which issecured to the output shaft 154. The reversing gear set 151 furtherincludes a ring gear 162; a carrier 164, held against rotation on thehousing 165 of drive unit 39; and a set of planet pinion 166, supportedon the carrier and meshing with ring gear 162 and sun gear 160.

When the selector sleeve 156 of coupler 152 is moved leftward, its dogteeth engage dog teeth 158 on a sun gear 160, secured to input 44,thereby producing a direct forward drive connection among output shaft154, rear drive shaft 18 and input shaft 44.

When the selector sleeve 156 of coupler 152 is moved rightward, its dogteeth engage dog teeth 168, which are secured to ring gear 162. With sungear 160 driven by the output 40 of transmission 42 and carrier 164 heldagainst rotation, ring gear 162, output shaft 154 and rear drive shaft18 are underdriven in a reverse direction relative to the speed anddirection of sun gear 160.

Coupler 170, secured to shaft 154, is located adjacent a forward drivemechanism 172 for transmitting power to forward driveshaft 20. Drivemechanism 172 may include a pinion 174, journalled on output shaft 154;an idler (not shown) meshing with pinion 174, and a gear 176 meshingwith the idler and secured to front driveshaft 20. When the selectorsleeve 178 of coupler 170 is moved leftward, its dog teeth engage dogteeth 180 on pinion 174, thereby producing a drive connection betweenoutput shaft 154 and forward driveshaft 20. Alternatively, drivemechanism 172 may include a first sheave, journalled on output shaft 154in the location of pinion 174; a second sheave secured to driveshaft 20and located in the position of gear 176; and a drive chain or belt 182,engaged with the first and second sheaves.

In accordance with the provisions of the patent statutes, the preferredembodiment has been described. However, it should be noted that thealternate embodiments can be practiced otherwise than as specificallyillustrated and described.

1. A drive unit located in a power path between a transmission outputand the wheels of a vehicle, comprising: a first gear set including afirst input driveably connected to the transmission output, and a firstoutput coupled by the first gearset to the first input, the first outputalternately rotating in a forward rotary direction and an underdrivenreverse rotary direction relative to a speed and a direction of thetransmission output; and a mechanism for driveably connecting the firstoutput to at least a first set of vehicle wheels.
 2. The drive unit ofclaim 1, wherein the first gear set includes: a first sun gear driveablyconnected to the transmission output; a first ring gear; a first carrierfixed against rotation; first planet pinions supported on the firstcarrier and meshing with the first sun gear and the first ring gear; anda first coupler supported on the first output for alternately driveablyconnecting the first output to the first ring gear and the first sungear.
 3. The drive unit of claim 1, wherein the first gear set includes:a first sun gear driveably connected to the transmission output; a firstring gear; a first carrier; first planet pinions supported on the firstcarrier and meshing with the first sun gear and the first ring gear; anda first coupler supported on the first carrier for alternately driveablyconnecting the first carrier to the first ring gear and holding thefirst carrier against rotation.
 4. The drive unit of claim 1, whereinthe mechanism further connects the first output to wheels located at thefront and rear of the motor vehicle.
 5. The drive unit of claim 1,wherein the first gear set includes: a first pinion driveably connectedto the transmission output; a layshaft; a first gear secured to thelayshaft and meshing with the first pinion; a second pinion secured tothe layshaft; a first output gear journalled on the first output; areverse idler meshing with the second pinion and second pinion; a firstcoupler secured to the first output for driveably connecting the firstoutput alternately to the first pinion and output gear.
 6. The driveunit of claim 1, further comprising: a differential mechanism includinga second input driveably connected to the first output, a firstdifferential output and a second differential output, said differentialmechanism dividing torque transmitted to the second input into a firsttorque portion transmitted to the front wheels from the firstdifferential output and a second torque portion transmitted to the rearwheels from the second differential output.
 7. The drive unit of claim1, further comprising: a first driveshaft; a second driveshaft; and adifferential mechanism that includes: a second sun gear driveablyconnected to the first driveshaft; a second ring gear driveablyconnected to the first driveshaft; a second carrier driveably connectedto the first output; second planet pinions supported on the secondcarrier and meshing with the second sun gear and the second ring gear.8. The drive unit of claim 1, further comprising: first and secondhalfshafts, each halfshaft driveably connected to one of a right-sidevehicle wheel and left-side vehicle wheel; a driveshaft; and adifferential mechanism that includes: bevel gear differential driveablyconnected to the first and second halfshafts; a second sun geardriveably connected to the bevel gear differential; a second ring geardriveably; a second carrier driveably connected to the first output;second planet pinions supported on the second carrier and meshing withthe second sun gear and the second ring gear; a bevel pinion driveablyconnected to the second ring gear; a gear meshing with the bevel pinionand driveably connected to the driveshaft.
 9. A drive unit located in apower path between a transmission output and the wheels of a vehicle,comprising: a gearset comprising: a first sun gear driveably connectedto the transmission output; a first ring gear; a first carrier; firstplanet pinions supported on the first carrier and meshing with the firstsun gear and the first ring gear; and a first coupler supported on thefirst carrier for alternately driveably connecting the first carrier tothe first ring gear and holding the first carrier against rotation;first and second halfshafts, each halfshaft driveably connected to oneof a right-side vehicle wheel and left-side vehicle wheel; driveshaft;and an inter-axle differential unit driveably connected to the first andsecond halfshafts, comprising: a second sun gear; driveably connected tothe bevel gear differential; a second ring gear; a second carrierdriveably connected to the first output; second planet pinions supportedon the second carrier and meshing with the second sun gear and thesecond ring gear. a bevel pinion driveably connected to the second ringgear; a bevel gear meshing with the bevel pinion and driveably connectedto the driveshaft.
 10. A drive unit located in a power path between atransmission output and the wheels of a vehicle, comprising: a firstdriveshaft; a second driveshaft; a first gear set that includes: a firstpinion driveably connected to the transmission output; a layshaft; afirst gear secured to the layshaft and meshing with the first pinion; asecond pinion secured to the layshaft; a first output gear journalled onthe first output; a reverse idler meshing with the second pinion andsecond pinion; a first coupler secured to the first output for driveablyconnecting the first output alternately to the first pinion and outputgear; and a differential mechanism that includes: a second sun geardriveably connected to the first driveshaft; a second ring geardriveably connected to the first driveshaft; a second carrier driveablyconnected to the first output; second planet pinions supported on thesecond carrier and meshing with the second sun gear and the second ringgear.
 11. A drive unit located in a power path between a transmissionoutput and the wheels of a vehicle, comprising: a first driveshaft; afirst gear set that includes: a first pinion driveably connected to thetransmission output; a layshaft; a first gear secured to the layshaftand meshing with the first pinion; a second pinion secured to thelayshaft; a first output gear journalled on the first output; a reverseidler meshing with the second pinion and second pinion; a first couplersecured to the first output for driveably connecting the first outputalternately to the first pinion and output gear; and a range mechanismcomprising a second coupler secured to the first output and a secondoutput, and a gear unit for underdriving the second output relative to aspeed of the first output, the second coupler driveably connecting thefirst output alternately to the gear unit and the first driveshaft. 12.The drive unit of claim 11, wherein the gear unit comprises: a rangepinion connectable by the second coupler to the first output; an idlersupported for rotation on the layshaft, the idler comprising a firstidler pinion meshing with the range pinion, and a second idler pinionsecured to the first idler pinion; and a second output gear meshing withthe second idler pinion; and a third coupler supported on the firstdriveshaft for coupling and decoupling the second output gear and thefirst driveshaft.
 13. (FIG. 2) The drive unit of claim 11, wherein: therange pinion is journalled on the first output; the second output gearis journalled on the first driveshaft; and further comprising a pilotbearing secured to the first driveshaft and supporting the first output.14. The drive unit of claim 11, further comprising: a second driveshaft;and wherein the gear unit further comprises a third output gear securedto the second driveshaft and meshing with the first idler pinion.